This invention relates to a method to reduce pressure drop of viscous materials flowing through pipes. More particularly, it relates to a method to reduce pressure drop in polyamide process piping.
By polyamide is meant nylon, particularly long chain polymeric amides having recurring amide linkages as an integral part of the polymer chain, and capable of being formed into a shaped structure such as a filament, film, or engineering plasticstype structure. Examples are nylon 6, nylon 6,6, nylon 4, nylon 6,10, and the like and blends thereof.
Attempts to reduce the pressure drop of viscous material flowing through pipes are not new. For instance, in 1904, Isaacs & Speed received a patent for conveying oil through an envelope of water, U.S. Pat. No. 759,374. In 1961, Charles, Govier, and Hodgson reported "The Horizontal Pipe Line Flow of Equal Density Oil-Water Mixtures". In 1964, J. C. Slattery did a theoretical analysis of "Two-Phase Annular Laminar Flow of Simple Fluids Through Cylindrical Tubes".
In U.S. Pat. No. 2,821,205 to Chilton et al., a method and apparatus for lubricating pipe lines is disclosed, primarily directed to use of water in oil pipe lines.
U.S. Pat. No. 3,040,760 to Macks describes a conduit having a foraminous liner which distributes high pressure gas in a thin layer on the internal surface of process piping to improve flow of viscous material.
The two above U.S. patents are both hereby incorporated by reference, in toto. The Macks invention is very complex and expensive and, therefore, not practical. In the processing of polyamides, the problems of reducing pressure drop through the process piping is complicated by the fact that the viscous polymer is very hot, and many materials are dissolved, destroyed, or miscible with the polymer. There has been no report of any work on viscous polymers at high temperature to reduce the pressure drop in the process piping.